Heat flask



A -1 1933- R. s. FERGUSON 1,920,853

HEAT FLASK Filed May 18. 1931 Patented Aug. 1, 1933 This invention relates to' heat flasks 1 for them 'p'eutic'and other uses',-'and it has for its general object the provision of axnormally hermetic casing containing a chemical normally in liquid state, havingthe property of changing its state with evolution of comparatively great heat when brought-into contactw'ithfa'ir, in conjunction with means controlling theacoess" of "air to the'chemicalatthewill'of the user,-. and automatically performing the necessary'functions inoident to the 'r'estorai'' of the. flask to its potential: condition.

ther objects of the invention will appear as the following description of a preferred and practical embodiment thereof proceeds.

g The exemplary form of the invention in the accompanying'drawing in which Figure l is-a'frontelevation;

is shown Figure 2 is a vertical 1 sectiontak'en along the line 2 =-2 =of Figure l; and a i Figure 3' is an 'enlargedfvertical sectional view through the'u'pper part of the flask including the valve-means. f r 5 Referring now in detail to the several figures in which" the'sarne characters of reference have been employed. throughout to designate identical parts, the numeral 1' represents a casing preferably formed of a. conductive material such as metal and being'preferably constructed in two concave or dished halves, 2 .and 3, withtheir open faces confronting and with a marginal portion,4, of one halfjpeened orturned over the marginal portion of the other half; The angular joint between the two halves is brazed or otherwise hermetically sealed. Its construction is such that if pres sure is at any time generated within the casing the expansive stress is borne not by the solder or brazing compound but by the over-turned marginal edge t, so that bursting of the casing is impossible with any pressure such as it is possible to generate, as will presently be more fully explained. I

At one point, preferably in its peripheral edge the casing is provided with an opening 5, into which the active chemical, represented by the mass 6, was initially introduced. This chemical. is of such anature that when reduced to liquid state andkept excluded from air it will remain in liquid state and inert in so far as the evolution of latent heat is concerned. When air is brought into contact with said chemical it crystallizes with a marked evolution of heat and when the mass 01 the chemical immediately contacted by the air is minimized, crystallization takes place instantaneously beginning at the point" of initial air contact and being immediately transmitted through the entire liquid mass, evolving a heat which can hardly be borne bythe hand'and which persists in proportion to the mass of chemical employed,

lasting a great deal-longer than would the same degree of heatin an equal amount of water. One of the preferred uses of the invention therefore,

is as a substitute fora hot peuticpractise. V V

While there are a number and compounds capable of giving up heat under water cattle in therathe conditions specified in connection with the present invention, I have found that a mixture of j sodium acetate with a small proportion of water is best" suitedto produce the desired result. In practice fourteen ounces of sodiumacetate are liquefied by heat and mixed with from two thirds of ah 'ounceto one ounce of water. t is to be understood that thesefproportions are empirical and that other proportions of water and sodium acetate may be used with satisfactory results.

Valve mechanism, which is generally designated by the reference character 7, is disposed in the opening 5,-said mechanismcomprising a shell including a bushing 8, brazed or otherwise hermetically secured to the casing. A cylindrical cup 9,

is soldered or otherwise secured to the bushing 8,

the lower end of the cup having a cylindrical eX- tension 10, of reduced diameter. A stem 11,

passes through the bushing, cup, and cylindrical extension. having a collar 12 fixed thereto and a-s'pring 13, housedwithin the cup 9 and Held in compression between the lower end of the bushing 8 and said collar. The bushing 8 is provided with an internal valve seat 14 and the stem is provided with a tapered valve 15 cooperating with said seat. The stem 11 is provided with at least one, and

preferably a plurality of shallow longitudinal grooves 16 forming air passages through the shell 7. l I

The spring 13 normally holds valve 15 against this seat 14 excluding air from the interior of the casing. When the stem is pulled outwardly by any convenient means, such for instance as" the ring 17, the valve 15 opens against the tension of the spring and permits a small quantity of air to flow throughthe grooves 16 into the chamber of the casing l. The lower end'of the stem 11 is provided with a flared head 18 of such diameter and external proportion as to engage the annular edge of the extension 10, closing the air passage and at the same time providing a stop to limit the outward pull of the stem 11. It, will thus be of known chemicals understood. that the period during which the small quantity of air is admitted to the casing 1 boiling it for awhile.

ment until the flared head 18 engages the end of the edge of the extension 10, a slight rubbing between said head andextension will occur, wiping ofi the surplus liquid, inducingrthe immediate formation of a crystal at-the point of rubbing, through the liquid chemical which has just been contacted by air admitted throughthe valve 15.

The formation of the initial crystal at once afiects sciously and without actual intent to slightly ro-.

tate the stem 11 providing the wiping action necessary to minimize the amount of chemical immediately contacted by the air. 7

When once the air has been" admitted, the crystallization taken place, and the heat generated, the ring 1'7 may be let go so asto; close the valve 15 and prevent the escape of any volatile product of the reaction. In view of the large mass of chemical used in the flask the heat will persist for several hours. When the flask cools the chemical willstill be in a solidified state and once again inert to the evolution of latent heat. The chemical is restored to its original potential condition by placing'the flask in boiling water and The chemical liquefies again, absorbing heat with great rapidity while liquefying. Whenthe boiling has reached the point at which a slight pressure, generally not exceeding two pounds above atmospheric pressure, has been generated in the casing the valve 15 will open slightly under pressure upon the flared head, 18 permitting .the outward passage of enough vapor to relieve the excess pressure. As soon as this release has taken place the valve 15 snaps shut under the urge of the spring 13.

Thus a bursting pressure cannot be realized in the flask. When the boiling has been carried on to the point at which the valve 15 is opened by the internal pressure the air admitted from the preceding operation of the device is driven out,

its place being taken by vapors from the chemical eventuating from the boiling. After a period of boiling, the length of which is indeterminate and may be ascertained by experiment, the chemical in liquefying has again stored the amount of heat which it had previously evolved in crystallizing, the flask may then be taken from the boiling water and permitted to cool and just so long as air is excluded from the flask the liquid will remain inert, and at atmospheric temperature, ready to be started again into heat evolution whenever the valve is reciprocally operated.

WhileI have in the above description disclosed what I ibelieve to be a preferred and practical form of the invention, it is to be understood that the details of construction as shown and described ,through,'having a valve engaging said seat and having a flared inner end extending beyond said shell adapted to engage the inner end of said shell in valve relation when said external valve is opened, said stem and shell providing an air passage communicating between the exterior of the casing and the interior of said casing in intermediate positionsjof said valve stem, a spring mounted in said shell normally holding said external valve closed, the means for operating said valve. 7

2. Heat flask asclaimed in claim 1, the shell comprising a bushing hermetically secured to said casing and a cup member constituting a spring housing screwed to said bushing.

RALPH s. FERGUSON. 

